Stackable flat bottomed can

ABSTRACT

The invention seeks to provide the possibility of producing alternately (according to need) on the same production line beverage cans which are in one piece in the body portion and alternatively thereto metal cans for in particular baby food or children&#39;s food, milk foods or evaporated milk, while at the same time affording the possibility of considerable material savings on the last-mentioned food sector. Proposed for that purpose is a metal can comprising a seamless can body of sheet metal comprising a can body portion and a substantially flat bottom formed in one piece therewith, wherein the body portion is drawn conically inwardly both towards the bottom and also towards its open end respectively. The substantially flat bottom has an outwardly facing bead or indentation for stackingly receiving a connecting seam which connects one end of the can body portion of a second identical metal can to the lid thereof.

The invention concerns a metal can of steel or aluminum, preferably of smaller format, as is usual for baby or children's food or evaporated milk. The metal can is a one-piece can of the stated kinds of sheet metal, wherein added as a second part is a lid which is fitted with a fold configuration at the upper edge of the can (more precisely: the body portion or lower portion or seamless can body).

Metal containers or cans are generally manufactured for the stated purposes from three parts (referred to as three-part cans): a body portion rolled from sheet metal, with a longitudinal seam connecting the axially extending end edges, together with a bottom and a lid which are connected to the open ends of the body portion by way of a respective double-fold seam. Production is admittedly simple and inexpensive but material-intensive.

Metals can are also already produced in two part form and used in particular as beverage cans. For that purpose the body portion and the bottom are produced in one piece by wall ironing (DWI process) and only the cover is applied by folding in the usual fashion. Manufacture is markedly more difficult and more complicated and expensive but markedly more advantageous in terms of material consumption. Because of the difficulties of and costs involved in manufacture, that kind of production is used predominantly in the field of beverage cans which are produced in large numbers, in which respect a production line provided for that purpose is often not sufficiently utilised to full capacity because of the specialisation to beverage cans.

The invention seeks to provide the possibility, and it is this that the invention considers to be its technical object, of producing alternately (also according to need) on the same production line beverage cans which are in one part in the body portion thereof, and alternatively metal cans for in particular baby food or children's foods, milk foods or evaporated milk, while at the same time seeking to afford the possibility of considerable material savings on the last-mentioned food sector.

That object is attained in accordance with claims 1 and 25 or also for the stacking condition in accordance with claim 20. In terms of its essence the production procedure for the metal can is adopted from the production of beverage cans so that production can be effected on the same production line. In particular however the bottom shape is adapted to the different purpose of use and is optimised to provide that optimum utilisation of the space volume becomes a possibility. Besides the retention of being capable of standing in a stable condition simple and secure stackability of the cans according to the invention is also achieved (claim 1 and claim 25).

That object is also attained by alternative uses (claim 26 and claim 27) of the filled can as set forth in claim 21 or claim 20. Evaporated milk is preferred, a foodstuff, as a non-carbonised filling material for the open can as set forth in claim 1 or the closed can as set forth in claim 20.

The can bottom is of a substantially flat configuration in contrast to two-part beverage cans current at the priority date. In that respect the can bottom does not have concave or convex curvatures (claim 4). Accordingly the filling volume of the small-volume can body portions substantially corresponds to the schematic space volume of the can (in the form of a cylindrical body) which is thus entirely available for filling.

To achieve stability in respect of shape an inert gas can also be introduced when filling the can and thus a slight increased internal pressure can be produced.

A preferred ‘slight increased pressure’ is in the region of 0.1 MPa (1 bar), in addition to the external pressure, preferably between 0.8 bar and 1.2 bar in relation to the external pressure which is generally to be assumed to be 1 bar (0.1 MPa) (claim 22), all at normal outside temperature. That is what is intended by ‘slight’. That is to be viewed in relation to high pressures which can occur in the case of beverage cans with a carbonised content in a situation of use of between 0.4 MPa (4 bars) and 0.8 MPa (8 bars) on the additionally allowed pressure which a bottom which is curved inwardly in a dome shape can withstand.

The claimed metal cans are of small volume (claim 18) but can be of different dimensions in terms of axial height, diameter and opening width at the end of the body portion. Their volume in terms of the significance of a ‘relatively small format’ is in the range of between 150 ml and 500 ml, that is to say less than half a liter, preferably less than 330 ml. Their height is generally no greater than 120 mm and their diameter is between 50 mm and 75 mm.

The axial extent of the conical portions (in the interpretation of a portion of a cone, that is to say in the form of a truncated cone, but certainly ‘conical’) at top and bottom can vary but they are clearly visible. A region in which the clearly visible cone shapes occur is dependent on the diameter of the can body portion. It can however be specified as being composite. At the top the angle of the cone surface is to be established in the range of 30±20% (claim 15). At the bottom the cone surface is inclined in the range of between 10° and 30° (claim 14), with in each case a corresponding axial length, to permit stacking.

The possible ways of increasing bottom stiffness (claims 5, 6 and 7) which are claimed for stiffening the substantially flat bottom surface can also be replaced by fine ribs or grooves or the like. It is essential in that respect that the bottom surface is substantially flat (free from outward curvature configurations). It can however have staggered annular shoulders in the form of a plurality of steps (claim 7).

The bottom is stiffened insofar as to avoid outward displacement for preventing stability when standing and for putting a block on stackability. The bottom is nonetheless flat, which as measured from the surface on which it stands allows it to extend upwardly no further than substantially 5 mm (claim 8). It extends in a height region between the surface on which it stands and the highest location of the surface of the bottom, generally in the central portion of the bottom, which does not extend upwardly further than a provided stacking bead arranged radially within the peripheral rib on which the can stands (claim 6).

In spite of the relatively flat configuration of the bottom it is stable in respect of pressure but not to the same extent as a bottom which is curved in a dome shape. Its stability in respect of pressure, against being displaced or curved outwardly, is up to substantially 2 bars, in particular 3.5 bars (claim 16). In the case of steel sheet metal, sheet metal thicknesses used for that purpose for the bottom are in the range of between 0.2 mm and 0.25 mm (claim 17).

The bottom stiffness is adapted to the purpose of use. A terrace-shaped configuration (claim 9) can be adopted as well as a central flat region surrounded by annularly extending corrugations (claim 10).

The method of stacking the seamless can bodies (claim 25) can also be interpreted in such a fashion that it concerns the manufacture of those can bodies. A substantially flat bottom is shaped in one piece. There is a conical inwardly drawn configuration at the respective axial ends of the can, both in the lower portion and also at the upper end portion. The substantially flat bottom adjoins a further outwardly disposed bead which can be referred to as the stacking bead. In the stacking condition or in the stacking operation, a connecting seam, disposed therebeneath, of a second can which is identical or structurally similar (possibly with different printing thereon and decoration) engages therein in stacking relationship. The same purpose is fulfilled by the peripherally extending indentation in the conical inwardly drawn portion which can be interpreted as a laterally open groove and can come into contact within the inside edge of a fold seam.

A substantially flat lid plate portion or surface of a lid which is fitted by a folded configuration is lowered with respect to the connecting seam and directly adjoins that seam by way of a damping bead (chuck wall) which projects axially relative to the interior of the can body portion or the closed container (claim 11). The degree of lowering is slight. Its dimension is less than the axial height of the fold configuration (claim 12).

The lid is in the form of a tear-open lid with a peripherally extending weakening line and a tear-open tab, preferably in the form of a full tear-open lid with a round weakening line near the damping bead or chuck wall (claim 13).

In the stacked condition (claim 20) the bottom bead which stands up axially inwardly (towards the interior of the closed container) and which is arranged radially within the lower end of the conical inwardly drawn portion of the body portion of the can is in stacking contact with a fold seam belonging to a subjacent can. The lower end of the inwardly drawn portion forms the support stand rib (claim 2).

What applies to the upwardly projecting bottom bead of the foregoing body portion is to be correspondingly applied to the radially further outwardly disposed peripheral inwardly shaped portion (in the form of an indentation) in the region of the frustoconical inwardly drawn portion of another can body portion (claim 3).

The peripherally extending inwardly shaped portion is disposed directly radially outwardly on the inwardly drawn portion. It is the radially outwardly facing wall or surface of the support stand rib (claim 3) which is shaped radially inwardly and thus ‘faces outwardly’.

Preferably the upwardly projecting bottom bead or peripheral inwardly shaped portion, while retaining the axially downwardly projecting support stand rib, goes directly from same or is at least near thereto.

Further advantageous features/properties are to be found in the appendant claims and are also described in connection with the description hereinafter of a number of embodiments by way of example.

Further features are described in greater detail in connection with the description hereinafter of a number of embodiments by way of example. In the accompanying drawings:

FIG. 1 is a diagrammatic view in section, including the axis 100 of the cans, showing the form of a new metal can in the case of a first embodiment by way of example, shortly prior to stacking engagement,

FIG. 2 is a similar view showing one of the cans of FIG. 1 in the condition of not yet being closed. The bottom 3 is the same,

FIG. 3 shows a perspective view illustrating the bottom 3 of the metal can of FIG. 1,

FIG. 4 is a similar view to FIG. 2 showing a modified embodiment, and

FIG. 5 is the same view as in FIG. 4 showing a further modified configuration.

The basic shape of the metal cans 1, 1 a or 15 of sheet metal as shown in FIGS. 1 through 3 comprises a seamless can body portion 2 with a bottom 3 formed in one piece thereon. At its two end regions the body portion 2 is drawn in, in a conical configuration (at the upper edge what is referred to as a necking, and at the lower edge an inwardly drawn portion to afford a peripherally extending support stand rib on which the can stand). The conical shape is shown at 5 or 11 at the respective axial end regions.

The open end 17 of the body portion 2 can be closed in the usual manner with a metallic lid 4 by way of a double-fold seam 12. In that way the upper closed axial end 2 b is formed. Production of the body portion and the bottom is effected in the usual manner by wall ironing (drawn wall ironed or DWI) and affords a marked saving on material, as is known from two-part beverage cans. The lid 4 has a ‘plate portion’ in the form of a lid panel 4 a and a peripherally extending damping bead or chuck wall 13 which goes over into the connecting seam 12 (for example in the form of a fold configuration). The panel 4 a is substantially flat and is lowered with respect to the upper end of the seam 12 and directly adjoins that seam 12 by way of the axially downwardly projecting bead 13.

The can bottom 3 is of a substantially flat configuration—in contrast to two-part beverage cans current at the priority date. It does not have any concave or convex curvature configurations. Accordingly the filling volume substantially corresponds to the schematic space volume of the can which is thus fully available for filling.

An axially outwardly projecting support stand rib 6 of small radius of curvature 6 a directly adjoins the lower end of the conical inwardly drawn portion 5 of the body portion 2. The bottom portions which are radially within that rib 6 are at a small spacing above the support stand plane E formed by the rib, on which the can stands. An axially outwardly open bead 7 directly adjoins the support rib 6 at the radial inward side thereof—. In relation to the position and the shape of the seam 12 between the opening edge of the body portion 2 and the cover closing the opening—the bead 7 is of such an arrangement and dimensions that the seam 12 of another similar can be reliably received in the bead 7 when stacking the metal cans one upon the other, and that contributes to easy reliable stackability. The axial alignment of the seam 12 and the bead 7 is symbolised by the line Y.

The annular plane defined by Y is in relation to the upper can 1 and the similar lower can 1 a. It is however equally also representative of the bead 7 and seam (fold configuration) 12′ on the same can 1. Reference 12′ symbolises the fold seam (not shown) on the upper can 1. It is as such also measurable on its own as stackable if it is placed in a stacking relationship with ‘one like it’ as is shown in respect of the beginning of the stacking condition as illustrated in FIG. 1. That also applies in the same manner for the examples shown hereinafter in FIGS. 4 and 5.

The bottom region within the bead 7 is of a terrace-shaped configuration and comprises the flat central surface 8 and two also flat annular surfaces 9 and 10 which are connected together by way of small steps or shoulders 9 a, 10 a. The step heights are less than the horizontal extents of the annular surfaces.

Overall therefore that gives a substantially flat structure for the bottom 3 which does not have any inwardly projecting curvature configurations. Neither those which appear in the center as a dome-shaped curvature configuration nor those which distributed in spaced relationship over the bottom represent dome-shaped individual curvature configurations in an array of a plurality of such curvature configurations.

In that respect the substantially flat bottom extends only limitedly in the heightwise direction, which explains its small spacing in relation to the support stand rib 6. The plane E in which the can is supported when standing is defined by the lowest point of the rib 6 which extends around the stack bead 7. The small radius of curvature 6 a defines the arc which defines the axially lower end of the support rib 6. Spaced therefrom in the axial direction (and also in the radial direction) is the central surface 8. Those two dimensions define the heightwise region of the bottom which is still deemed to be ‘substantially flat’. That heightwise region or the difference in height is not greater than 10 mm, preferably being less than 5 mm, measured from the support plane E (the lower axial end of the support rib 6) and the highest location of the bottom 3 which in FIG. 1 corresponds to the central surface region 8.

In the case of steel cans, the gauge of the sheet metal used is between 0.2 mm and 0.25 mm. The bottom, in spite of the absence of dome-shaped reinforcement portions, is so adapted as to withstand an internal pressure which extends in the region up to 3.5 bars (0.35 MPa), wherein that is the differential pressure between the internal pressure in a closed and filled can and the external pressure beneath the bottom.

That resistance to pressure relates to a resistance to being pushed out or curved out, minor fluctuations in the heightwise positions of the portions of the terrace-shaped bottom are certainly permitted, but the capability on the part of the can to stand up and its stackability are not to be adversely affected, which circumscribes the maximum movements of the substantially flat bottom in respect of its small heightwise dimension. It will be appreciated that this provides that the bottom remains stabilised even up to substantially 2 bars (0.20 MPa), that is to say even at lower pressures it does not suffer outward displacement or adopt an outwardly curved configuration, in relation to the same pressure difference which was specified with the numeral value of 3.5 bars.

The metal cans are of small volume, they can involve different dimensions in respect of axial height 15 a, diameter 15 b and opening width 15 c at the can body portion neck 17 (axial upper end). Their volume is preferably in the range of between 150 ml and 500 ml. Their height is generally no greater than 120 mm, their diameter is between 50 mm and 75 mm. The axial extent 6 c of the conical inwardly drawn portion 5 of the body portion 2 at the transition to the bottom region can vary, and likewise the conical inclination 6 b.

The conical inclination 6 b is in relation to the axially lower end of the can. It is in an illustrated angle 6 b which can be selected to be between 10° and 30°, depending on the diameter 15 b of the can body portion. The cone inclination at the oppositely disposed end, symbolically indicated by 11 in FIG. 1 (in the case of the axially underneath can) is above the angle inclination at the lower end and is 30° with a range of ±20%.

To achieve stability in respect of shape the can, after filling with the food or in the filling operation, can be provided with an inert gas which produces a slight internal increased pressure. A preferred ‘slight increased pressure’ is of the order of magnitude of 1 bar (0.1 MPa), in addition to the external pressure, preferably between 0.8 bar and 1.2 bar in relation to the external pressure which is generally to be assumed to be 1 bar. The gauge of the body portion 2, which is associated in that respect, is in the range of between 0.07 mm and 0.09 mm sheet metal gauge, particularly when using steel metal sheet.

FIG. 4 shows a modified configuration 3 a of a bottom region within the support rib 6 of a can 20, the rib 6 directly adjoining the cone surface. In this case also the central portion 22 is smooth and flat. The portion 21 between that and the support rib 6 is slightly corrugated or is of a zig-zag configuration in cross-section, wherein once again the support rib 6 is adjoined by an outwardly open bead 7 in which—as indicated—the fold seam on the lid 24 of the subjacent can is received. The gripping tab 25 serving to open the can is disposed on the lid. It will be apparent that this bottom 22 is also substantially flat without convex or concave curvature configurations. The corrugated portion 21 has a plurality of peripherally extending depressions 23 which however are not convex/concave curvature configurations in the sense of a dome or an eccentric outwardly curved configuration. The amplitudes of the depressions are smaller than the depth of the bead 7. At the upper open end the can 20 has a conical inwardly drawn portion 41 with a substantially flat inclined surface. A lid can be fitted by a folded configuration to the body portion neck 47, as is shown in the form of the lid 24 in FIG. 4.

The container 30 shown in FIG. 5 has an inner bottom surface 35 which corresponds to that of the bottom 3 a in FIG. 4. As already described hereinbefore, disposed directly radially within the support bead 36 of the can is an outwardly open bead 38 for possibly receiving the seam of another can.

In this configuration, provided at the radial outside surface of the support bead 36, that is to say in the region of a conical inwardly drawn portion 31, is an indentation 32 (in the form of a bead which is open at the edge side) and which is so arranged and is of such dimensions that it can reliably receive the seam 34 provided at the upper end 30 b between the lid 33 and a can 30 a disposed therebeneath, of larger diameter.

The peripheral indentation 32 at the radial outside surface of the support bead 36 can be present on its own or in addition to the peripheral bead 38, the latter corresponding to the bead 7 of the previous examples. The relationship of the inwardly drawn portions 41, 31 determines the size of a lid 36 which is involved, to achieve stacking. Either by engagement of the fold seam 34 in the radially outwardly disposed inwardly shaped configuration or by engagement into the radially inwardly disposed bead 38 (corresponding to bead 7 in the other examples). Both, the bead 7 or 38 on the one hand and the inwardly shaped configuration 32 on the other hand, are ‘facing outwardly’. They can be provided individually or cumulatively.

The possible ways of increasing the degree of bottom stiffness, which are show for stiffening the inner bottom region, can also be replaced by fine ribs or grooves or the like. In that case the bottom still remains substantially flat and free from curvature configurations which in the case of a beverage can is referred to as a ‘dome-shaped’ inwardly curved configuration.

The information set forth in relation to the preceding embodiments regarding the addition of pressurised inert gas for stabilising the wall, the sheet metal gauges, the small height of the substantially flat bottom, the dimensions of the conical inwardly drawn portions and the pressure stability of the bottom, is to be correspondingly applied to the structures shown in FIGS. 4 and 5. They equally apply here.

The drawings do not show notch lines in the lid plate portion of a respective lid 4, 24 or 33. They are familiar to the man skilled in the art and serve to open the lid, so that they are not shown in the drawing. In that case, a respective lid has, as a tear-open lid, a peripherally extending weakening line which can be broken open with the tear-open tab 25 shown in FIG. 4 or FIG. 5 in order to remove the lid plate portion within the peripherally extending weakening line. That is usual and conventional state of the art which is not to be separately described in detail here. 

1. A metal can comprising a seamless can body (1) of sheet metal having a can body portion (2) and a—substantially flat—bottom (3; 3 a; 35) formed in one piece therewith, wherein the body portion (2) is drawn conically inwardly (5, 11; 31, 41) both towards the bottom (3) and also towards its open end (15 c) respectively and the substantially flat bottom (3) has an outwardly facing bead (7) or indentation (32), adapted and suitable for stackingly receiving a connecting seam (12; 34) which connects an end (15 c) of a can body portion of a second identical metal can (1 a; 15) to the lid (4) thereof.
 2. A metal can as set forth in claim 1 wherein the axially inwardly projecting bottom bead (7) is arranged radially within the lower end of the conical inwardly drawn portion (5) of the body portion (2) and—preferably forming an axially outwardly projecting support rib (6)—starts from the conical inwardly drawn portion (5) or is at least near thereto.
 3. A metal can as set forth in claim 1 wherein the indentation (32) is provided in the region of the conical inwardly drawn portion (31) of the body portion (30) radially outside an axially outwardly projecting support rib (36) directly adjoining the inwardly drawn portion.
 4. A metal can as set forth in one of the preceding claims wherein the—substantially flat—bottom (3) is free from convexly or concavely curved bottom portions.
 5. A metal can as set forth in one of claims 1 through 4 wherein the—substantially flat—bottom (3) comprises a plurality of radially mutually displaced, substantially flat bottom surface portions (8, 9, 10).
 6. A metal can as set forth in one of the preceding claims wherein the flat bottom (3; 3 a; 35) extends in a heightwise region which is defined by an axially upper end of the bead (7) and an axially lower end of a support rib (6), in particular in a heightwise region of less than 5 mm.
 7. A metal can as set forth in previous claim 5 wherein the bottom surface portions are respectively connected together by way of narrow shoulders (9 a, 10 a) or the like steps, in particular the ‘narrow shoulders’ are shorter than a lateral extent of a respectively adjacent bottom surface portion, which represents a slight stepping.
 8. A metal can as set forth in claim 5 wherein the bottom (3; 3 a; 35) does not project axially inwardly higher than 5 mm, measured from a lower axial end of a support rib (6, 36).
 9. A metal can as set forth in claim 5 wherein the flat bottom surface portions (8, 9, 10) are displaced relative to each other in the axial direction by way of shoulders (9 a, 10 a), preferably in an axially inward direction when viewing from radially outside to radially inside.
 10. A metal can as set forth in one of claims 1 through 9 wherein the substantially flat bottom (21), outside a bottom center (22; 8), has annularly extending corrugations (23) or the like, in particular of a slight amplitude.
 11. A metal can as set forth in one of the preceding claims wherein a substantially flat lid panel (4 a, lid plate portion) is lowered with respect to the connecting seam (12) and directly adjoins said seam by way of an axially inwardly projecting damping bead (13).
 12. A metal can as set forth in the preceding claim wherein the degree of lowering in relation to the connecting seam is slight, in terms of heightwise dimension less than an axial height of a double fold configuration (12).
 13. A metal can as set forth in claim 1 or claim 6 wherein the lid (4, 24) is in the form of a tear-open lid with peripherally extending weakening line and tear-open tab (25).
 14. A metal can as set forth in claim 1 wherein the conical inwardly drawn portion (5) is between 10° and 30° relative to the bottom (3).
 15. A metal can as set forth in claim 1 or claim 14 wherein the conical inwardly drawn portion (11, 41) is in the range of 30°±20% towards the open end (47).
 16. A metal can as set forth in claim 1 or claim 6 wherein the substantially flat bottom has a pressure resistance to being displaced outwardly or to being caused to adopt an outwardly curved configuration, which extends to substantially two bars (0.20 MPa), as a differential pressure in relation to an outside pressure.
 17. A metal can as set forth in claim 16 wherein the sheet metal of the substantially flat bottom is between 0.2 mm and 0.25 mm in thickness.
 18. A metal can as set forth in one of the preceding claims wherein the receiving volume of the can extends between 250 ml to substantially 500 ml.
 19. A metal can as set forth in claim 16 wherein the pressure resistance extends to substantially 0.35 MPa.
 20. A closed metal can comprising a seamless can body (1) of sheet metal, (i) having a can body portion (2) and a substantially flat bottom (3) which is shaped in one piece therewith, and closed with a lid (4, 24, 33), wherein a substantially flat lid panel (4 a) of the lid is lowered with respect to a connecting seam (12) to the can body portion; wherein (ii) the lid panel (4 a) directly adjoins the connecting seam by way of an axially inwardly projecting damping bead (13); (iii) the body portion (2) is respectively inclinedly drawn (5, 11; 31, 41) in both towards the bottom (3) and also towards its end (2 b) closed with the lid; and (iv) the substantially flat bottom (3; 3 a; 35) has an outwardly facing bead (7) or indentation (32) for stackingly receiving a connecting seam (12; 34) of a second identical metal can (1 a, 30 a), which connecting seam connects an axial end (30 b) of the further downwardly stacked can body portion to its lid (4, 33).
 21. A metal can as set forth in claim 20 comprising features of the can as set forth in one of claims 1 through
 19. 22. A metal can as set forth in claim 20 which is filled with a non-carbonised food, and is provided with an internal additional pressure due to an inert gas of more than 08 bar (0.08 MPa) above an external pressure.
 23. A metal can as set forth in claim 20 wherein the flat bottom (3; 3 a; 35) is of a maximum height of less than 10 mm above a support plane (E).
 24. A metal can as set forth in claim 20 or claim 23 wherein the maximum height is less than 5 mm.
 25. A method of producing or stacking one or more metal can or cans comprising a seamless can body (1) of sheet metal, having a can body portion (2) and a substantially flat bottom (3; 3 a; 35) which is formed in one piece therewith, wherein the body portion (2) is in a condition of or becomes conically inwardly drawn (5, 11; 31, 41) both towards the bottom and also towards its open end (17) respectively and the substantially flat bottom acquires an outwardly facing bead (7) or indentation (32) and receives a further downwardly disposed connecting seam (12; 34), which seam connects an axial end (17) of a can body portion of a second metal can (1 a, 30), which is identical in that respect, to the lid (4, 33) thereof, and the two cans are or become stacked.
 26. Use of a metal can as set forth in one of the preceding claims for children's food of various kinds.
 27. Use of a metal can as set forth in one of the preceding claims under claim 25 for evaporated milk or other milk products. 